These sensors are for cutting off the power in case a panic stop happens. Stop pedaling in pedal assist system may not be as quick as squeezing brake levers. In regular brakes you may need to have this double safety feature. Hydraulic brakes are typically powerful enough to stop you if a panic happens. It is not a mandatory by regulations and you can try your ebike without installing the cut-off and decide if you need it to be installed.
Do we have to install the brake cut-off sensors?